1. Field of the Invention
This invention relates to a boat hull having a bow, a stern, and a keel along its bottom extending from the bow toward the stern and more particularly to a tunnel structure along the bottom of the boat hull in the form of a truncated hollow partial cone indentation parallel to the keel of the boat. The cone indentation begins near the apex of the cone and extends toward the stern of the boat where the base of the cone is secured to the stern or transom of the boat hull. The partial cone shaped tunnel accomodates the rotary propeller of the boat and the drive shaft to the propeller from the interior of the boat.
2. Description of the Prior Art
Prior art patents have disclosed the use of tunnel shapes along the keel of a boat for several different purposes. Mostly the prior art structures were intended to produce desireable wake patterns for water skiing, as in U.S. Pat. No. 4,392,448xe2x80x94Shirley, to overcome the tendency of turning the boat as the propeller rotates, as in U.S. Pat. No. 3,745,963xe2x80x94Fisher, and to converge water flow and increase water pressure aft of the propeller, as in U.S. Pat. No. 4,622,016xe2x80x94Hankley. The prior art has not directed the hull design to the desire to increase the efficiency of the drive from the boat""s motor to the propeller through the hull and to increase efficiency of driving the boat when in planing attitude. In an inboard powered boat, it is desireable to have the axis of the propeller drive shaft as near as possible to parallel to the keel of the boat. It is also desireable to place the driven propeller in its most efficient alignment with the water surface during initial acceleration and after the boat has attained its planing attitude or speed. The prior art has not addressed the angle of the propeller drive shaft exit from the hull of the boat and the angle of the propeller drive shaft to the hull of the boat at the position of the propeller when in driving contact with the water.
The present invention is a modification of the hull of a boat by installing a concave partial cone shaped section along the hull with the propeller shaft running near the central axis of the partial cone shape. The partial cone shaped section produces a slot or tunnel indentation running longitudinally from the keel, where the propeller shaft exits through the bottom of the hull, to the transom at the stern of the boat. The slot or tunnel is aligned at an angle of approximately 6xc2x0 to 12xc2x0 upward from the keel and toward the transom. The angle and length of the slot is related to the diameter of the propeller which rotates in the slot and is related to the length of the propeller drive shaft. In the design of the present invention, the propeller shaft exits from the keel of the boat at about 1xc2x0 to 5xc2x0 down from the lay of the keel, depending upon the configuration of the bottom of the boat. The relationship of the angle of the slot to the keel and the exit angle of the propeller shaft is calculated to place about 45% to 50% of the propeller turning inside the cone slot tunnel when the boat is at its planing speed and attitude. The connection of the cone near its apex to the hull causes air to be introduced into the cone along with water to produce an air slot at the hull.
The purpose of the partial cone shaped tunnel slot of the present invention in the hull of a boat is three fold. The cone shaped air slot allows the suction of the water to be broken at planing through cruising speeds, making it a surface drive, but safer because all of the components are under the boat, unlike other existing surface drives. The cone shaped air slot allows the propeller shaft to be mounted almost parallel to the lay of the keel of the bottom of the boat. The cone shaped air slot and the alignment of the propeller shaft in the slot allows the boat to be operated in shallower waters, increases efficiency and reduces fuel consumption.
It is an object of the present invention to improve the efficiency of a boat by modifying the bottom of the boat to permit desired angles of cone-to-keel and propeller-to-keel in the boat hull.
A further object in accord with the preceding object is the formation of a partial cone shaped hollow tunnel slot along the hull of a boat with a continuous cone angle from the lay of the keel to the transom of the boat.
A further object in accord with the preceding object is to provide a truncation of the cone shaped tunnel slot at about its apex to provide an improved angle of exit of a propeller shaft from inside the boat to the inside of the slot.
A further object in accord with the preceding object is to align the axis of the cone slot and the angle of the keel of the boat to provide for the propeller shaft to exit the boat and into the tunnel at almost parallel to the keel.
Further objects and features of the invention will be readily apparent to those skilled in the art from the appended drawings and specification illustrating preferred embodiments wherein: